Estimation of absolute and relative body fat content using non-invasive surrogates: Can DXA be bypassed?

Authors: GREENBLATT, DAVID - Tufts University; BRUNO, CHRISTOPHER - Emerald Lake Safety, Llc; HARMATZ, JEROLD - Tufts University; DAWSON-HUGHES, BESS - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; ZHANG, QINGCHEN - Tufts University; LI, CHUNHUI - Tufts University; CHOW, CHRISTINA - Emerald Lake Safety, Llc

Submitted to: Journal of Clinical Pharmacology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2023
Publication Date: 11/9/2023
Citation: Greenblatt, D.J., Bruno, C.D., Harmatz, J.S., Dawson-Hughes, B., Zhang, Q., Li, C., Chow, C.R. 2023. Estimation of absolute and relative body fat content using non-invasive surrogates: Can DXA be bypassed? Journal of Clinical Pharmacology. https://doi.org/10.1002/jcph.2306.
DOI: https://doi.org/10.1002/jcph.2306

Interpretive Summary: Dual-energy X-ray absorptiometry (DXA) scans determine body composition, but these scanners are expensive and not always available in clinical practice. Several aspects of body size including weight, height, and waist circumference are easily measured. This study was done to determine whether any of these body size measurements, together with age, could substitute for assessments of body fat determined by DXA scans. DXA and body size measurements from a cohort of 9,230 randomly-selected Americans, available through the ongoing National Health and Nutrition Examination Survey (NHANES), were used to evaluate the combination of age, height, weight, and waist circumference as predictors of DXA-determined absolute and relative body fat content. There was a very strong association (93% for males and 96% for females) between the combination of age, height, total weight, and waist circumference with DXA measured total body fat. Body fat calculated with use of these 4 simple measures appears to be accurate enough to substitute for DXA-derived total body fat in many clinical situations.

Technical Abstract: Dual-energy X-ray absorptiometry (DXA) scanning is used for objective determination of body composition, but instrumentation is expensive and not generally available in customary clinical practice. Anthropometric surrogates are often substituted as anticipated correlates of absolute and relative body fat content in the clinical management of obesity and its associated medical risks. DXA and anthropometric data from a cohort of 9230 randomly-selected American subjects, available through the ongoing National Health and Nutrition Examination Survey (NHANES), was used to evaluate surrogate combinations of (age, height, total weight, waist circumference) as predictors of DXA-determined absolute and relative body fat content. Multiple regression analysis yielded linear combinations of the 4 surrogates that were closely predictive of DXA-determined absolute fat content (R^2= 0.93 and 0.96 for males and females), and improved over customary surrogate-based predictors such as body mass index. However prediction of relative body fat was less robust (R^2 < 0.75). The paradigm was validated using an independent cohort from NHANES, as well as two independent external subject groups. The described regression-based algorithm is likely to be accurate enough to substitute for DXA-scanning in many clinical situations. Further work is needed to assess algorithm validity for subgroups of individuals with "atypical" body construction.